Field of the Invention
The invention relates to a swing rotor type centrifuge (centrifugal separator) used for separating a sample in the fields of medicine, pharmacy, genetic engineering, biotechnology, and so on, and particularly relates to an improvement in the shape of a swing rotor that holds swinging buckets.
Description of Related Art
A centrifugal separator is a device, which includes a rotor capable of accommodating a plurality of sample containers filled with samples therein and a driving means, such as a motor, rotationally driving the rotor and rotates the rotor in a rotor chamber to apply a centrifugal force so as to centrifugally separate the samples. A swing rotor for centrifuge is a device for rotating buckets, which accommodate sample containers having a bottomed part and filled with samples therein, in a state of holding the buckets swingable with respect to the swing rotor body. A centrifugal load of the bucket is held by a set of holding pins (convex parts) disposed on opposite surfaces of arms of the swing rotor body. Concave parts are formed on two side surfaces of the bucket to engage with the cylindrical surfaces on the outer peripheral side of the holding pins of the swing rotor body, and the concave parts are hung downward from the top of the holding pins and are held by the holding pins in a slidable manner. A gap that does not interfere with the sliding exists between the front end surfaces of the holding pins and the opposite surfaces of the concave parts of the bucket (orthogonal plane). In terms of the positional relationship, the central axis of the bucket and the driving shaft of the motor are parallel to each other (swing angle θ=0°) when the rotor is stationary. However, as the rotation speed of the rotor increases, the bucket swings due to the centrifugal force. The bucket rotates around the swing axis so that θ>0°, and then enters a substantially horizontal state (θ≈90°) when a rotation speed that is sufficient for generating a centrifugal force to make the bucket horizontal is reached. Thereafter, the centrifugal separation operation ends, and the swing angle θ decreases as the rotation speed drops and becomes 0° (θ=0°) when the rotation of the rotor stops. Thus, the relative angle between the central axis of the bucket and the driving shaft of the swing rotor changes according to the centrifugal force during the centrifugation.
The load of the bucket, the sample, and the sample container during the centrifugation is held by the convex parts (holding pins) that are disposed to face each other on the swing rotor body. When the swing rotor body rotates at a high speed, the holding pins are slightly deformed by the centrifugal force they receive from the bucket, and particularly stress is concentrated near the bases of the convex parts. For this reason, various measures have been considered in order to prevent the stress from concentrating on a particular portion of the holding pins. According to Japanese Patent Publication No. 2012-101203, for example, the holding pin 25 has a shape that is narrowed down to reduce the outer diameter on the aim side, and the diameter of the sliding surface in contact with the pin receiving part of the bucket is increased, and a narrowed shape is formed on the front end side of the sliding surface, so as to prevent the stress received by the holding pins from concentrating on a particular portion while maintaining the contact area of the bucket and the holding pins at a certain level.